[PATCH v6 0/2] drm: bridge: Add TI tmds181 and sn65dp159 driver

[PATCH v6 0/2] drm: bridge: Add TI tmds181 and sn65dp159 driver

[Mike Looijmans]

In the past I've seen (and contributed to) hacks that model the chips as
phy or even (really!) clock drivers. Since the chip usually sits between
a signal that is (almost) HDMI and a HDMI connector, I decided to stop
lying and write it as a DRM bridge driver.

Our experience with these chips is that they work best under manual control
enabling them only once the signal is active. At low resolutions (under 4k),
the optimal setting is usually to only use redriver mode. Setting the
termination to 150-300 Ohms improves EMC performance at lower resolutions,
hence the driver enables 75-150 Ohms for HDMI2 modes and defaults to
150-300 Ohm termination for other modes.


Changes in v6:
Rename ti,mode to ti,retimer-mode
Add DRM_DISPLAY_HDMI_HELPER to Kconfig
Change "ti,mode" to "ti,retimer-mode"

Changes in v5:
ti,equalizer and ti,mode changed to enum
Rename ti,slew-rate to slew-rate
Make properties conditional for DP159/TMDS181
Remove ti,dvi-mode (always set to avoid conflict)
Really added vcc/vdd regulator support
"oe" gpio is now "reset" (reversed logic)
devicetree enums ti,equalizer and ti,mode
Always disable HDMI_SEL (formerly "dvi-mode")

Changes in v4:
Use fallback compatible
dev_err_probe, this_module, of_match_ptr
Use fallback compatible
Add vcc-supply and vdd-supply

Changes in v3:
Fix duplicate links
Add vcc-supply and vdd-supply
Fix missing type for ti,slew-rate
Lower-case hex values and use defines for EYESCAN registers
Remove equalizer code (unlikely to be used)
Remove attributes (no longer useful, undocumented)
Fix build for 6.17 kernel
Use devm_drm_bridge_alloc
Sort includes and add linux/bitfield.h
Check chip type and complain on mismatch

Changes in v2:
Document driver specific bindings like slew-rate and threshold
Use atomic_enable/disable
Use #defines for bit fields in registers
Allow HDMI 2 compliance
Filter modes on clock range
Use cross-over pixel frequency instead of manual overides
Devicetree bindings according to standards

Mike Looijmans (2):
  dt-bindings: drm/bridge: ti-tmds181: Add TI TMDS181 and SN65DP159
    bindings
  drm: bridge: Add TI tmds181 and sn65dp159 driver

 .../bindings/display/bridge/ti,tmds181.yaml   | 170 +++++++
 drivers/gpu/drm/bridge/Kconfig                |  12 +
 drivers/gpu/drm/bridge/Makefile               |   1 +
 drivers/gpu/drm/bridge/ti-tmds181.c           | 427 ++++++++++++++++++
 4 files changed, 610 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/ti,tmds181.yaml
 create mode 100644 drivers/gpu/drm/bridge/ti-tmds181.c

-- 
2.43.0

base-commit: 53e760d8949895390e256e723e7ee46618310361
branch: drm-ti-tmds181

Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


TOPIC Embedded Products B.V.
Materiaalweg 4, 5681 RJ Best
The Netherlands

T: +31 (0) 499 33 69 69
E: mike.looijmans@topic.nl
W: www.topic.nl

Please consider the environment before printing this e-mail

[PATCH v6 1/2] dt-bindings: drm/bridge: ti-tmds181: Add TI TMDS181 and SN65DP159 bindings

[Mike Looijmans]

Add DT binding document for TI TMDS181 and SN65DP159 HDMI retimers.

The two chips have similar register maps, but different applications
(source vs. sink).

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>

---

Changes in v6:
Rename ti,mode to ti,retimer-mode

Changes in v5:
ti,equalizer and ti,mode changed to enum
Rename ti,slew-rate to slew-rate
Make properties conditional for DP159/TMDS181
Remove ti,dvi-mode (always set to avoid conflict)

Changes in v4:
Use fallback compatible

Changes in v3:
Fix duplicate links
Add vcc-supply and vdd-supply
Fix missing type for ti,slew-rate

Changes in v2:
Document driver specific bindings like slew-rate and threshold

 .../bindings/display/bridge/ti,tmds181.yaml   | 170 ++++++++++++++++++
 1 file changed, 170 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/ti,tmds181.yaml

diff --git a/Documentation/devicetree/bindings/display/bridge/ti,tmds181.yaml b/Documentation/devicetree/bindings/display/bridge/ti,tmds181.yaml
new file mode 100644
index 000000000000..9b23221634bb
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/bridge/ti,tmds181.yaml
@@ -0,0 +1,170 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/bridge/ti,tmds181.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: TMDS181 and SN65DP159 HDMI retimer/redriver chips
+
+maintainers:
+  - Mike Looijmans <mike.looijmans@topic.nl>
+
+description: |
+  Texas Instruments TMDS181 and SN65DP159 retimer and redriver chips.
+  https://www.ti.com/product/TMDS181
+  https://www.ti.com/product/SN65DP159
+  When I2C control is enabled, various pin strapping options like equalizer and
+  slew-rate are unavailable. These can be configured through I2C using the
+  properties defined here.
+  A common application for these chips is to convert AC coupled serdes outputs
+  from an FPGA or SoC into HDMI compliant signals.
+
+properties:
+  compatible:
+    oneOf:
+      - const: ti,tmds181
+      - items:
+          - const: ti,sn65dp159
+          - const: ti,tmds181
+
+  reg:
+    enum:
+      - 0x5b
+      - 0x5c
+      - 0x5d
+      - 0x5e
+
+  reset-gpios:
+    maxItems: 1
+    description: GPIO specifier for OE pin which acts as active low reset.
+
+  vdd-supply:
+    description: Core power supply, 1.1V
+
+  vcc-supply:
+    description: IO power supply, 3.3V
+
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/$defs/port-base
+        unevaluatedProperties: false
+        description: Video port for HDMI (ish) input
+
+        properties:
+          endpoint:
+            $ref: /schemas/media/video-interfaces.yaml#
+            unevaluatedProperties: false
+
+      port@1:
+        $ref: /schemas/graph.yaml#/$defs/port-base
+        unevaluatedProperties: false
+        description: Video port for HDMI output (panel or bridge)
+
+        properties:
+          endpoint:
+            $ref: /schemas/media/video-interfaces.yaml#
+            unevaluatedProperties: false
+
+    required:
+      - port@0
+      - port@1
+
+  ti,retimer-mode:
+    enum:
+      - source
+      - sink
+    description:
+      Force chip to operate in "source" or "sink" mode.
+
+  ti,retimer-threshold-hz:
+    minimum: 25000000
+    maximum: 600000000
+    default: 200000000
+    description:
+      Cross-over point. Up until this pixel clock frequency the chip remains in
+      the low-power redriver mode. Above the threshold the chip should operate
+      in retimer mode.
+
+  slew-rate:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 0
+    maximum: 3
+    default: 3
+    description: Set slew rate, 0 is slowest, 3 is fastest.
+
+  ti,equalizer:
+    enum:
+      - adaptive
+      - disabled
+      - fixed
+    default: adaptive
+    description: Configure the equalizer
+
+if:
+  properties:
+    compatible:
+      contains:
+        const: ti,sn65dp159
+
+then:
+  properties:
+    ti,retimer-mode:
+      default: source
+
+else:
+  properties:
+    ti,retimer-mode:
+      default: sink
+    slew-rate: false
+
+required:
+  - compatible
+  - reg
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        bridge@5b {
+            compatible = "ti,sn65dp159", "ti,tmds181";
+            reg = <0x5b>;
+            vdd-supply = <&vcc_1v1_reg>;
+            vcc-supply = <&vcc_3v3_reg>;
+            reset-gpios = <&gpio2 1 GPIO_ACTIVE_LOW>;
+            slew-rate = <2>;
+            ti,retimer-threshold-hz = <350000000>;
+            ti,retimer-mode = "source";
+            ti,equalizer = "disabled";
+
+            ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                port@0 {
+                    reg = <0>;
+
+                    endpoint {
+                        remote-endpoint = <&encoder_out>;
+                    };
+                };
+
+                port@1 {
+                    reg = <1>;
+
+                    endpoint {
+                        remote-endpoint = <&hdmi_connector_in>;
+                    };
+                };
+            };
+        };
+    };
-- 
2.43.0


Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


TOPIC Embedded Products B.V.
Materiaalweg 4, 5681 RJ Best
The Netherlands

T: +31 (0) 499 33 69 69
E: mike.looijmans@topic.nl
W: www.topic.nl

Please consider the environment before printing this e-mail

Re: [PATCH v6 1/2] dt-bindings: drm/bridge: ti-tmds181: Add TI TMDS181 and SN65DP159 bindings

[Rob Herring (Arm)]

On Mon, 22 Sep 2025 14:18:44 +0200, Mike Looijmans wrote:
> Add DT binding document for TI TMDS181 and SN65DP159 HDMI retimers.
> 
> The two chips have similar register maps, but different applications
> (source vs. sink).
> 
> Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
> 
> ---
> 
> Changes in v6:
> Rename ti,mode to ti,retimer-mode
> 
> Changes in v5:
> ti,equalizer and ti,mode changed to enum
> Rename ti,slew-rate to slew-rate
> Make properties conditional for DP159/TMDS181
> Remove ti,dvi-mode (always set to avoid conflict)
> 
> Changes in v4:
> Use fallback compatible
> 
> Changes in v3:
> Fix duplicate links
> Add vcc-supply and vdd-supply
> Fix missing type for ti,slew-rate
> 
> Changes in v2:
> Document driver specific bindings like slew-rate and threshold
> 
>  .../bindings/display/bridge/ti,tmds181.yaml   | 170 ++++++++++++++++++
>  1 file changed, 170 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/bridge/ti,tmds181.yaml
> 

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>

[PATCH v6 2/2] drm: bridge: Add TI tmds181 and sn65dp159 driver

[Mike Looijmans]

The tmds181 and sn65dp159 are "retimers" and hence can be considered
HDMI-to-HDMI bridges. Typical usage is to convert the output of an
FPGA into a valid HDMI signal, and it will typically be inserted
between an encoder and hdmi-connector.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
---

Changes in v6:
Add DRM_DISPLAY_HDMI_HELPER to Kconfig
Change "ti,mode" to "ti,retimer-mode"

Changes in v5:
Really added vcc/vdd regulator support
"oe" gpio is now "reset" (reversed logic)
devicetree enums ti,equalizer and ti,mode
Always disable HDMI_SEL (formerly "dvi-mode")

Changes in v4:
dev_err_probe, this_module, of_match_ptr
Use fallback compatible
Add vcc-supply and vdd-supply

Changes in v3:
Lower-case hex values and use defines for EYESCAN registers
Remove equalizer code (unlikely to be used)
Remove attributes (no longer useful, undocumented)
Fix build for 6.17 kernel
Use devm_drm_bridge_alloc
Sort includes and add linux/bitfield.h
Check chip type and complain on mismatch

Changes in v2:
Use atomic_enable/disable
Use #defines for bit fields in registers
Allow HDMI 2 compliance
Filter modes on clock range
Use cross-over pixel frequency instead of manual overides
Devicetree bindings according to standards

 drivers/gpu/drm/bridge/Kconfig      |  12 +
 drivers/gpu/drm/bridge/Makefile     |   1 +
 drivers/gpu/drm/bridge/ti-tmds181.c | 427 ++++++++++++++++++++++++++++
 3 files changed, 440 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/ti-tmds181.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index b9e0ca85226a..d679180b05b1 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -430,6 +430,18 @@ config DRM_TI_SN65DSI86
 	help
 	  Texas Instruments SN65DSI86 DSI to eDP Bridge driver
 
+config DRM_TI_TMDS181
+        tristate "TI TMDS181 and SN65DP159 HDMI retimer bridge driver"
+	depends on OF
+	select DRM_KMS_HELPER
+	select DRM_DISPLAY_HDMI_HELPER
+	select REGMAP_I2C
+	help
+	  Enable this to support the TI TMDS181 and SN65DP159 HDMI retimers.
+	  The SN65DP159 provides output into a cable (source) whereas the
+	  TMDS181 is meant to forward a cable signal into a PCB (sink). Either
+	  can be set up as source or sink though.
+
 config DRM_TI_TPD12S015
 	tristate "TI TPD12S015 HDMI level shifter and ESD protection"
 	depends on OF
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index 245e8a27e3fc..f4b5089e903c 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_DRM_TI_SN65DSI83) += ti-sn65dsi83.o
 obj-$(CONFIG_DRM_TI_SN65DSI86) += ti-sn65dsi86.o
 obj-$(CONFIG_DRM_TI_TDP158) += ti-tdp158.o
 obj-$(CONFIG_DRM_TI_TFP410) += ti-tfp410.o
+obj-$(CONFIG_DRM_TI_TMDS181) += ti-tmds181.o
 obj-$(CONFIG_DRM_TI_TPD12S015) += ti-tpd12s015.o
 obj-$(CONFIG_DRM_NWL_MIPI_DSI) += nwl-dsi.o
 obj-$(CONFIG_DRM_ITE_IT66121) += ite-it66121.o
diff --git a/drivers/gpu/drm/bridge/ti-tmds181.c b/drivers/gpu/drm/bridge/ti-tmds181.c
new file mode 100644
index 000000000000..cda2d20e4990
--- /dev/null
+++ b/drivers/gpu/drm/bridge/ti-tmds181.c
@@ -0,0 +1,427 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * TI tmds181 and sn65dp159 HDMI redriver and retimer chips
+ *
+ * Copyright (C) 2018 - 2025 Topic Embedded Products <www.topic.nl>
+ *
+ * based on code
+ * Copyright (C) 2007 Hans Verkuil
+ * Copyright (C) 2016, 2017 Leon Woestenberg <leon@sidebranch.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_crtc.h>
+#include <drm/display/drm_hdmi_helper.h>
+#include <drm/drm_print.h>
+#include <drm/drm_probe_helper.h>
+
+MODULE_DESCRIPTION("I2C device driver for DP159 and TMDS181 redriver/retimer");
+MODULE_AUTHOR("Mike Looijmans");
+MODULE_LICENSE("GPL");
+
+#define TMDS181_REG_ID		0
+#define TMDS181_REG_REV		0x8
+#define TMDS181_REG_CTRL9	0x9
+/* Registers A and B have a volatile bit, but we don't use it, so cache is ok */
+#define TMDS181_REG_CTRLA	0xa
+#define TMDS181_REG_CTRLB	0xb
+#define TMDS181_REG_CTRLC	0xc
+#define TMDS181_REG_EQUALIZER	0xd
+/* EYESCAN registers don't appear to deserve separate names */
+#define TMDS181_REG_EYESCAN_E	0xe
+#define TMDS181_REG_EYESCAN_F	0xf
+#define TMDS181_REG_EYESCAN_15	0x15
+#define TMDS181_REG_EYESCAN_17	0x17
+#define TMDS181_REG_EYESCAN_1F	0x1f
+#define TMDS181_REG_AUX		0x20
+
+
+#define TMDS181_CTRL9_SIG_EN			BIT(4)
+#define TMDS181_CTRL9_PD_EN			BIT(3)
+#define TMDS181_CTRL9_HPD_AUTO_PWRDWN_DISABLE	BIT(2)
+#define TMDS181_CTRL9_I2C_DR_CTL		GENMASK(1, 0)
+
+#define TMDS181_CTRLA_MODE_SINK			BIT(7)
+#define TMDS181_CTRLA_HPDSNK_GATE_EN		BIT(6)
+#define TMDS181_CTRLA_EQ_ADA_EN			BIT(5)
+#define TMDS181_CTRLA_EQ_EN			BIT(4)
+#define TMDS181_CTRLA_AUX_BRG_EN		BIT(3)
+#define TMDS181_CTRLA_APPLY			BIT(2)
+#define TMDS181_CTRLA_DEV_FUNC_MODE		GENMASK(1, 0)
+
+#define TMDS181_CTRLB_SLEW_CTL			GENMASK(7, 6)
+#define TMDS181_CTRLB_HDMI_SEL_DVI		BIT(5)
+#define TMDS181_CTRLB_TX_TERM_CTL		GENMASK(4, 3)
+#define TMDS181_CTRLB_DDC_DR_SEL		BIT(2)
+#define TMDS181_CTRLB_TMDS_CLOCK_RATIO_STATUS	BIT(1)
+#define TMDS181_CTRLB_DDC_TRAIN_SET		BIT(0)
+
+#define TMDS181_CTRLB_TX_TERM_150_300_OHMS	1
+#define TMDS181_CTRLB_TX_TERM_75_150_OHMS	3
+
+#define TMDS181_CTRLC_VSWING_DATA		GENMASK(7, 5)
+#define TMDS181_CTRLC_VSWING_CLK		GENMASK(4, 2)
+#define TMDS181_CTRLC_HDMI_TWPST1		GENMASK(1, 0)
+
+#define TMDS181_EQ_DATA_LANE			GENMASK(5, 3)
+#define TMDS181_EQ_CLOCK_LANE			GENMASK(2, 1)
+#define TMDS181_EQ_DIS_HDMI2_SWG		BIT(0)
+
+/* Above this data rate HDMI2 standards apply (TX termination) */
+#define HDMI2_PIXEL_RATE_KHZ	340000
+
+enum tmds181_chip {
+	tmds181,
+	dp159,
+};
+
+struct tmds181_data {
+	struct i2c_client *client;
+	struct regmap *regmap;
+	struct drm_bridge *next_bridge;
+	struct drm_bridge bridge;
+	u32 retimer_threshold_khz;
+};
+
+static inline struct tmds181_data *
+drm_bridge_to_tmds181_data(struct drm_bridge *bridge)
+{
+	return container_of(bridge, struct tmds181_data, bridge);
+}
+
+static int tmds181_attach(struct drm_bridge *bridge, struct drm_encoder *encoder,
+			  enum drm_bridge_attach_flags flags)
+{
+	struct tmds181_data *data = drm_bridge_to_tmds181_data(bridge);
+
+	return drm_bridge_attach(encoder, data->next_bridge, bridge, flags);
+}
+
+static enum drm_mode_status
+tmds181_mode_valid(struct drm_bridge *bridge, const struct drm_display_info *info,
+		   const struct drm_display_mode *mode)
+{
+	unsigned long long rate;
+
+	rate = drm_hdmi_compute_mode_clock(mode, 8, HDMI_COLORSPACE_RGB);
+
+	/* Minimum clock rate is 25MHz */
+	if (rate < 25000000)
+		return MODE_CLOCK_LOW;
+
+	/*
+	 * When in HDMI 2 mode, the clock is 1/40th of the bitrate. The limit is
+	 * then the data rate of 6Gbps, which would use a 600MHz pixel clock.
+	 */
+	if (rate > 600000000)
+		return MODE_CLOCK_HIGH;
+
+	return MODE_OK;
+}
+
+static void tmds181_enable(struct drm_bridge *bridge, struct drm_atomic_state *state)
+{
+	struct tmds181_data *data = drm_bridge_to_tmds181_data(bridge);
+	const struct drm_crtc_state *crtc_state;
+	const struct drm_display_mode *mode;
+	struct drm_connector *connector;
+	struct drm_crtc *crtc;
+	unsigned int val;
+
+	/*
+	 * Retrieve the CRTC adjusted mode. This requires a little dance to go
+	 * from the bridge to the encoder, to the connector and to the CRTC.
+	 */
+	connector = drm_atomic_get_new_connector_for_encoder(state,
+							     bridge->encoder);
+	crtc = drm_atomic_get_new_connector_state(state, connector)->crtc;
+	crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
+	mode = &crtc_state->adjusted_mode;
+
+	/* Set retimer/redriver mode based on pixel clock */
+	val = mode->clock > data->retimer_threshold_khz ? TMDS181_CTRLA_DEV_FUNC_MODE : 0;
+	regmap_update_bits(data->regmap, TMDS181_REG_CTRLA,
+			   TMDS181_CTRLA_DEV_FUNC_MODE, val);
+
+	/* Configure TX termination based on pixel clock */
+	val = mode->clock > HDMI2_PIXEL_RATE_KHZ ?
+				TMDS181_CTRLB_TX_TERM_75_150_OHMS :
+				TMDS181_CTRLB_TX_TERM_150_300_OHMS;
+	regmap_update_bits(data->regmap, TMDS181_REG_CTRLB,
+			   TMDS181_CTRLB_TX_TERM_CTL,
+			   FIELD_PREP(TMDS181_CTRLB_TX_TERM_CTL, val));
+
+	regmap_update_bits(data->regmap, TMDS181_REG_CTRL9,
+			   TMDS181_CTRL9_PD_EN, 0);
+}
+
+static void tmds181_disable(struct drm_bridge *bridge, struct drm_atomic_state *state)
+{
+	struct tmds181_data *data = drm_bridge_to_tmds181_data(bridge);
+
+	/* Set the PD_EN bit */
+	regmap_update_bits(data->regmap, TMDS181_REG_CTRL9,
+			   TMDS181_CTRL9_PD_EN, TMDS181_CTRL9_PD_EN);
+}
+
+static const struct drm_bridge_funcs tmds181_bridge_funcs = {
+	.attach		= tmds181_attach,
+	.mode_valid	= tmds181_mode_valid,
+	.atomic_enable	= tmds181_enable,
+	.atomic_disable	= tmds181_disable,
+
+	.atomic_reset = drm_atomic_helper_bridge_reset,
+	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
+};
+
+static const u8 tmds181_id_tmds181[8] __nonstring = "TMDS181 ";
+static const u8 tmds181_id_dp159[8]   __nonstring = "DP159   ";
+
+static int tmds181_check_id(struct tmds181_data *data, enum tmds181_chip *chip)
+{
+	int ret;
+	int retry;
+	u8 buffer[8];
+
+	for (retry = 0; retry < 20; ++retry) {
+		ret = regmap_bulk_read(data->regmap, TMDS181_REG_ID, buffer,
+				       sizeof(buffer));
+		if (!ret)
+			break;
+
+		/* Compensate for very long OE power-up delays due to the cap */
+		usleep_range(5000, 10000);
+	}
+
+	if (ret) {
+		dev_err(&data->client->dev, "I2C read ID failed\n");
+		return ret;
+	}
+
+	if (memcmp(buffer, tmds181_id_tmds181, sizeof(buffer)) == 0) {
+		dev_info(&data->client->dev, "Detected: TMDS181\n");
+		*chip = tmds181;
+		return 0;
+	}
+
+	if (memcmp(buffer, tmds181_id_dp159, sizeof(buffer)) == 0) {
+		dev_info(&data->client->dev, "Detected: DP159\n");
+		*chip = dp159;
+		return 0;
+	}
+
+	dev_err(&data->client->dev, "Unknown ID: %*pE\n", (int)sizeof(buffer), buffer);
+
+	return -ENODEV;
+}
+
+static bool tmds181_regmap_is_volatile(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	/* IBERT result and status registers, not used yet */
+	case TMDS181_REG_EYESCAN_15:
+	case TMDS181_REG_EYESCAN_17 ... TMDS181_REG_EYESCAN_1F:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct regmap_config tmds181_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.cache_type = REGCACHE_RBTREE,
+	.max_register = TMDS181_REG_AUX,
+	.volatile_reg = tmds181_regmap_is_volatile,
+};
+
+static const char * const tmds181_supplies[] = {
+	"vdd", "vcc"
+};
+
+static int tmds181_probe(struct i2c_client *client)
+{
+	struct tmds181_data *data;
+	struct gpio_desc *reset_gpio;
+	enum tmds181_chip chip;
+	const char *str;
+	int ret;
+	u32 param;
+	u8 val;
+
+	/* Check if the adapter supports the needed features */
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -EIO;
+
+	data = devm_drm_bridge_alloc(&client->dev, struct tmds181_data, bridge,
+				     &tmds181_bridge_funcs);
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	data->client = client;
+	i2c_set_clientdata(client, data);
+	data->regmap = devm_regmap_init_i2c(client, &tmds181_regmap_config);
+	if (IS_ERR(data->regmap))
+		return PTR_ERR(data->regmap);
+
+	/* The "OE" pin acts as a reset */
+	reset_gpio = devm_gpiod_get_optional(&client->dev, "reset",
+					     GPIOD_OUT_HIGH);
+	if (IS_ERR(reset_gpio))
+		return dev_err_probe(&client->dev, PTR_ERR(reset_gpio),
+				     "failed to acquire 'reset' gpio\n");
+
+	/* Enable power supplies while reset is active */
+	ret = devm_regulator_bulk_get_enable(&client->dev,
+					     ARRAY_SIZE(tmds181_supplies),
+					     tmds181_supplies);
+	if (ret)
+		return dev_err_probe(&client->dev, ret,
+				     "Failed to enable power supplies\n");
+
+	if (reset_gpio) {
+		/* Need at least 100us reset pulse */
+		usleep_range(100, 200);
+		gpiod_set_value_cansleep(reset_gpio, 0);
+	}
+
+	/* Reading the ID also provides time for the reset */
+	ret = tmds181_check_id(data, &chip);
+	if (ret)
+		return ret;
+
+	/*
+	 * We take care of power control, so disable the chips PM functions, and
+	 * allow the DDC to run at 400kHz
+	 */
+	regmap_update_bits(data->regmap, TMDS181_REG_CTRL9,
+			TMDS181_CTRL9_SIG_EN | TMDS181_CTRL9_PD_EN |
+			TMDS181_CTRL9_HPD_AUTO_PWRDWN_DISABLE |
+			TMDS181_CTRL9_I2C_DR_CTL,
+			TMDS181_CTRL9_PD_EN |
+			TMDS181_CTRL9_HPD_AUTO_PWRDWN_DISABLE |
+			TMDS181_CTRL9_I2C_DR_CTL);
+
+	/* Apply configuration changes */
+	if (!of_property_read_string(client->dev.of_node, "ti,retimer-mode", &str)) {
+		if (!strcmp(str, "source"))
+			val = 0;
+		else if (!strcmp(str, "sink"))
+			val = TMDS181_CTRLA_MODE_SINK;
+		else
+			return -EINVAL;
+		regmap_update_bits(data->regmap, TMDS181_REG_CTRLA,
+				   TMDS181_CTRLA_MODE_SINK, val);
+	}
+
+	/*
+	 * Using the automatic modes of the chip uses considerable power as it
+	 * will keep the PLL running at all times. So instead, define our own
+	 * threshold for the pixel rate. This also allows to use a sane default
+	 * of 200MHz pixel rate for the redriver-retimer crossover point, as the
+	 * modes below 3k don't show any benefit from the retimer.
+	 */
+	data->retimer_threshold_khz = 200000;
+	if (!of_property_read_u32(client->dev.of_node,
+				  "ti,retimer-threshold-hz", &param))
+		data->retimer_threshold_khz = param / 1000;
+
+	/* Default to low-power redriver mode */
+	regmap_update_bits(data->regmap, TMDS181_REG_CTRLA,
+			   TMDS181_CTRLA_DEV_FUNC_MODE, 0);
+
+	/* Default is adaptive equalizer */
+	val = TMDS181_CTRLA_EQ_EN | TMDS181_CTRLA_EQ_ADA_EN;
+	if (!of_property_read_string(client->dev.of_node, "ti,equalizer", &str)) {
+		if (!strcmp(str, "disabled"))
+			val = 0;
+		else if (!strcmp(str, "fixed"))
+			val = TMDS181_CTRLA_EQ_EN;
+		else if (!strcmp(str, "adaptive"))
+			val = TMDS181_CTRLA_EQ_EN | TMDS181_CTRLA_EQ_ADA_EN;
+		else
+			return -EINVAL;
+		regmap_update_bits(data->regmap, TMDS181_REG_CTRLA,
+				   TMDS181_CTRLA_EQ_EN | TMDS181_CTRLA_EQ_ADA_EN,
+				   val);
+	}
+
+	switch (chip) {
+	case dp159:
+		/*
+		 * Disable the "Adaptor ID block" on the DDC interface, which
+		 * could conflict with this driver.
+		 */
+		val = TMDS181_CTRLB_HDMI_SEL_DVI;
+		if (!of_property_read_u32(client->dev.of_node, "slew-rate",
+					  &param)) {
+			if (param > 3)
+				return dev_err_probe(&client->dev, -EINVAL,
+						     "invalid slew-rate\n");
+			/* Implement 0 = slow, 3 = fast slew rate */
+			val |= FIELD_PREP(TMDS181_CTRLB_SLEW_CTL, (3 - param));
+		}
+		break;
+	default:
+		val = TMDS181_CTRLB_DDC_DR_SEL;
+		break;
+	}
+
+	/* Default to low-speed termination */
+	val |= FIELD_PREP(TMDS181_CTRLB_TX_TERM_CTL, TMDS181_CTRLB_TX_TERM_150_300_OHMS);
+
+	ret = regmap_write(data->regmap, TMDS181_REG_CTRLB, val);
+	if (ret < 0) {
+		dev_err(&client->dev, "regmap_write(B) failed\n");
+		return ret;
+	}
+
+	/* Find next bridge in chain */
+	data->next_bridge = devm_drm_of_get_bridge(&client->dev, client->dev.of_node, 1, 0);
+	if (IS_ERR(data->next_bridge))
+		return dev_err_probe(&client->dev, PTR_ERR(data->next_bridge),
+				     "Failed to find next bridge\n");
+
+	/* Register the bridge. */
+	data->bridge.of_node = client->dev.of_node;
+
+	return devm_drm_bridge_add(&client->dev, &data->bridge);
+}
+
+static const struct i2c_device_id tmds181_id[] = {
+	{ "tmds181", },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, tmds181_id);
+
+#if IS_ENABLED(CONFIG_OF)
+static const struct of_device_id tmds181_of_match[] = {
+	{ .compatible = "ti,tmds181", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, tmds181_of_match);
+#endif
+
+static struct i2c_driver tmds181_driver = {
+	.driver = {
+		.name	= "tmds181",
+		.of_match_table = tmds181_of_match,
+	},
+	.probe		= tmds181_probe,
+	.id_table	= tmds181_id,
+};
+
+module_i2c_driver(tmds181_driver);
-- 
2.43.0


Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


TOPIC Embedded Products B.V.
Materiaalweg 4, 5681 RJ Best
The Netherlands

T: +31 (0) 499 33 69 69
E: mike.looijmans@topic.nl
W: www.topic.nl

Please consider the environment before printing this e-mail

Re: [PATCH v6 2/2] drm: bridge: Add TI tmds181 and sn65dp159 driver

[Dmitry Baryshkov]

On Mon, Sep 22, 2025 at 02:18:45PM +0200, Mike Looijmans wrote:
> The tmds181 and sn65dp159 are "retimers" and hence can be considered
> HDMI-to-HDMI bridges. Typical usage is to convert the output of an
> FPGA into a valid HDMI signal, and it will typically be inserted
> between an encoder and hdmi-connector.
> 
> Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
> ---
> 
> Changes in v6:
> Add DRM_DISPLAY_HDMI_HELPER to Kconfig
> Change "ti,mode" to "ti,retimer-mode"
> 
> Changes in v5:
> Really added vcc/vdd regulator support
> "oe" gpio is now "reset" (reversed logic)
> devicetree enums ti,equalizer and ti,mode
> Always disable HDMI_SEL (formerly "dvi-mode")
> 
> Changes in v4:
> dev_err_probe, this_module, of_match_ptr
> Use fallback compatible
> Add vcc-supply and vdd-supply
> 
> Changes in v3:
> Lower-case hex values and use defines for EYESCAN registers
> Remove equalizer code (unlikely to be used)
> Remove attributes (no longer useful, undocumented)
> Fix build for 6.17 kernel
> Use devm_drm_bridge_alloc
> Sort includes and add linux/bitfield.h
> Check chip type and complain on mismatch
> 
> Changes in v2:
> Use atomic_enable/disable
> Use #defines for bit fields in registers
> Allow HDMI 2 compliance
> Filter modes on clock range
> Use cross-over pixel frequency instead of manual overides
> Devicetree bindings according to standards
> 
>  drivers/gpu/drm/bridge/Kconfig      |  12 +
>  drivers/gpu/drm/bridge/Makefile     |   1 +
>  drivers/gpu/drm/bridge/ti-tmds181.c | 427 ++++++++++++++++++++++++++++
>  3 files changed, 440 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/ti-tmds181.c
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index b9e0ca85226a..d679180b05b1 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -430,6 +430,18 @@ config DRM_TI_SN65DSI86
>  	help
>  	  Texas Instruments SN65DSI86 DSI to eDP Bridge driver
>  
> +config DRM_TI_TMDS181
> +        tristate "TI TMDS181 and SN65DP159 HDMI retimer bridge driver"
> +	depends on OF
> +	select DRM_KMS_HELPER

Do you need it here?

> +	select DRM_DISPLAY_HDMI_HELPER

missing select DRM_DISPLAY_HELPER

> +	select REGMAP_I2C
> +	help
> +	  Enable this to support the TI TMDS181 and SN65DP159 HDMI retimers.
> +	  The SN65DP159 provides output into a cable (source) whereas the
> +	  TMDS181 is meant to forward a cable signal into a PCB (sink). Either
> +	  can be set up as source or sink though.
> +
>  config DRM_TI_TPD12S015
>  	tristate "TI TPD12S015 HDMI level shifter and ESD protection"
>  	depends on OF

-- 
With best wishes
Dmitry

Re: [PATCH v6 2/2] drm: bridge: Add TI tmds181 and sn65dp159 driver

[Mike Looijmans]

On 9/25/25 05:51, Dmitry Baryshkov wrote:
> On Mon, Sep 22, 2025 at 02:18:45PM +0200, Mike Looijmans wrote:
>> The tmds181 and sn65dp159 are "retimers" and hence can be considered
>> HDMI-to-HDMI bridges. Typical usage is to convert the output of an
>> FPGA into a valid HDMI signal, and it will typically be inserted
>> between an encoder and hdmi-connector.
>>
>> Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
>> ---
>>
>> Changes in v6:
>> Add DRM_DISPLAY_HDMI_HELPER to Kconfig
>> Change "ti,mode" to "ti,retimer-mode"
>>
>> Changes in v5:
>> Really added vcc/vdd regulator support
>> "oe" gpio is now "reset" (reversed logic)
>> devicetree enums ti,equalizer and ti,mode
>> Always disable HDMI_SEL (formerly "dvi-mode")
>>
>> Changes in v4:
>> dev_err_probe, this_module, of_match_ptr
>> Use fallback compatible
>> Add vcc-supply and vdd-supply
>>
>> Changes in v3:
>> Lower-case hex values and use defines for EYESCAN registers
>> Remove equalizer code (unlikely to be used)
>> Remove attributes (no longer useful, undocumented)
>> Fix build for 6.17 kernel
>> Use devm_drm_bridge_alloc
>> Sort includes and add linux/bitfield.h
>> Check chip type and complain on mismatch
>>
>> Changes in v2:
>> Use atomic_enable/disable
>> Use #defines for bit fields in registers
>> Allow HDMI 2 compliance
>> Filter modes on clock range
>> Use cross-over pixel frequency instead of manual overides
>> Devicetree bindings according to standards
>>
>>   drivers/gpu/drm/bridge/Kconfig      |  12 +
>>   drivers/gpu/drm/bridge/Makefile     |   1 +
>>   drivers/gpu/drm/bridge/ti-tmds181.c | 427 ++++++++++++++++++++++++++++
>>   3 files changed, 440 insertions(+)
>>   create mode 100644 drivers/gpu/drm/bridge/ti-tmds181.c
>>
>> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
>> index b9e0ca85226a..d679180b05b1 100644
>> --- a/drivers/gpu/drm/bridge/Kconfig
>> +++ b/drivers/gpu/drm/bridge/Kconfig
>> @@ -430,6 +430,18 @@ config DRM_TI_SN65DSI86
>>   	help
>>   	  Texas Instruments SN65DSI86 DSI to eDP Bridge driver
>>   
>> +config DRM_TI_TMDS181
>> +        tristate "TI TMDS181 and SN65DP159 HDMI retimer bridge driver"
>> +	depends on OF
>> +	select DRM_KMS_HELPER
> Do you need it here?

Yes, compiling a kernel without it results in:
ld: drivers/gpu/drm/bridge/ti-tmds181.o:(.rodata+0x2f8): undefined 
reference to `drm_atomic_helper_bridge_duplicate_state'
ld: drivers/gpu/drm/bridge/ti-tmds181.o:(.rodata+0x2fc): undefined 
reference to `drm_atomic_helper_bridge_destroy_state'
ld: drivers/gpu/drm/bridge/ti-tmds181.o:(.rodata+0x30c): undefined 
reference to `drm_atomic_helper_bridge_reset'

>
>> +	select DRM_DISPLAY_HDMI_HELPER
> missing select DRM_DISPLAY_HELPER

Will add in v7


>
>> +	select REGMAP_I2C
>> +	help
>> +	  Enable this to support the TI TMDS181 and SN65DP159 HDMI retimers.
>> +	  The SN65DP159 provides output into a cable (source) whereas the
>> +	  TMDS181 is meant to forward a cable signal into a PCB (sink). Either
>> +	  can be set up as source or sink though.
>> +
>>   config DRM_TI_TPD12S015
>>   	tristate "TI TPD12S015 HDMI level shifter and ESD protection"
>>   	depends on OF


-- 
Mike Looijmans